Biologist’s Study of Coyote Habits Has Practical Applications for Man

Times Staff Writer

When William Wirtz II set out to study the habits of coyotes, he had no idea he would eventually find himself theorizing about the relative merits of garbage can lids in Glendale and Claremont.

But one topic led to the other for the Pomona College biologist, who presented his ideas about coyotes and municipal sanitation at the recent convention of the American Assn. for the Advancement of Science.

The result is that Claremont officials find themselves reaping unexpected praise for what was part of a labor-saving experiment--using garbage cans with permanently attached lids--which led to de facto wildlife control by making it difficult for coyotes to scavenge through trash.

And in Glendale, where a 3-year-old girl was killed by a coyote in 1981, some officials say they want to look into Wirtz’s ideas.


Big Gap in Quantities Eaten

Wirtz’s analysis of coyote droppings and stomach contents of dead animals, showed that coyotes in the Glendale area apparently eat about 15 times as much human-generated trash as do coyotes in Claremont. The tightly fitted hinged lids on trash cans in Claremont were apparently causing that gap.

“I didn’t know this would happen,” Wirtz, a bearded, pipe-smoking assistant professor, said the other day in his office, which is decorated with stuffed animals. “The only explanation is the difference in the garbage cans. That seems to me to be a reasonable explanation for the data I have.”

He stressed that he’s not picking on Glendale, which has taken other steps to discourage coyotes from going into urbanized areas. Like Glendale, most cities allow garbage cans with tops easily dislodged by animals. Claremont began requiring the hinged-topped cans as part of a switch to automated, one-man trash trucks three years ago.


But Wirtz wants all foothill cities to know that trying to get rid of coyotes by killing them is “a waste of time, like trying to kill flies around a dead horse.”

Access to Food Key Factor

Most attacks by coyotes on household pets and people occur in neighborhoods where coyotes have easy access to household garbage have lost their innate fear of humans. Because coyotes are so territorial, other coyotes will fill the vacuum left by trapping of the animals in those areas. A better idea is to get rid of what attracted the animals to the area in the first place, Wirtz says.

Besides, he said, slaughtering coyotes could disrupt the ecological balance and cause a population boom in the small animals they eat, such as rabbits, rats and squirrels. And those animals can cause their own share of annoyances and health problems.


“That’s why I’m in favor of managing resources so it’s not suitable for coyotes, instead of killing coyotes,” he said, adding, however, that he would not hesitate to kill a vicious coyote as he had to do with one given to him as a pup. He still keeps another as a pet but makes sure it’s chained when strangers visit.

The City of Claremont helped fund Wirtz’s study, but both he and city officials emphasize that that had no bearing on his findings. In fact, the study was begun before the new garbage cans were purchased.

City Manager Len Wood said the hinged-topped plastic barrels, which hold 90 gallons and are on wheels, are required for the city’s new one-man trucks. Those trucks have an arm that lifts and empties the cans, allowing a reduction in the number of work crews and in back injuries to workers.

Trash Barrels Cost $61


The barrels cost the city $61 each and one is provided to each household as part of regular service. Even with the capital spending for trucks and cans, fees for curbside household pickup have dropped from $7.90 to $6.75 a month since the new trucks arrived, sanitation officials said. Backyard pickup rates have risen from $7.90 to $9.70 because that requires extra labor, they said.

The new trucks and cans are used in three-fourths of Claremont and the city is so pleased with the results that the system is to be expanded soon to include the entire city, Wood said. As for Wirtz’s claims that the cans also discourage coyotes from settling in Claremont residential neighborhoods, Wood said: “It’s fascinating but it’s really an unexpected benefit.”

In Glendale, John Bingham, administrative analyst in the city manager’s office, said that Wirtz’ theory “sounds like something we’d be interested in checking out, if, indeed, it’s valid.” But he and other officials said that problems with coyotes seem to have diminished sharply in recent years as residents follow a city ordinance and use common sense by not feeding coyotes, not leaving food outdoors for pets, not leaving small pets outdoors at night and making sure that food wastes are properly wrapped to conceal odors.

In addition, parks in the Glendale foothills now have heavy metal trash barrels with attached lids to discourage scavenging, and the city has put water drinking stations for wildlife in areas remote from residences.


Glendale Police Capt. Thomas Rutkoske said that, after the mauling death of 3-year-old Kelly Keen in August, 1981, the city undertook an extensive campaign to educate citizens on how to keep coyotes away.

“In the last three years, we’ve had zero calls about coyotes,” said Rutkoske, who headed the investigation into the child’s death and lives in a hillside area of Burbank that also had its share of coyotes. “Its extraordinarily quiet. I’m not saying the coyotes are not here, but I know I haven’t seen any and we are not getting any calls.” The captain said he wants to read a copy of Wirtz’s study before commenting on it.

Glendale Conditions Different

Lino Torres, Glendale’s sanitation supervisor, said he is familiar with the Claremont trucks but said that they work best in places with wide streets, relatively low population density and little on-street parking. They would be very difficult to use in the crowded, narrower streets of downtown and southern Glendale, he said. To use the hinged-top cans without the automated trucks, Torres said, could be dangerous to sanitation workers. “That’s something hanging out there for him to wrestle with,” he said.


Glendale residents are supposed to make sure lids are on their cans. “It is difficult to get everyone to comply,” Torres conceded, adding that he welcomes any ideas that “would keep the animal from tipping over cans and helping himself.”

Wirtz, who is 47 and has a Ph.D. in ecology and evolutionary biology from Cornell University, says he never intended to become a coyote expert, let alone one on garbage cans. If anything, his first love is birds of prey, like eagles and great horned owls; he and his wife, Helen, are well-known in wildlife circles for the clinic they run at their Mt. Baldy home where they have nursed more than 1,000 birds.

But Wirtz became interested in coyotes and their incursion into cities during research about birds and small mammals in the chaparral areas of the Angeles National Forest about 11 years ago. “I wanted to learn about who ate my mice,” he recalled.

Raised $4,000 for Research


After a number of increasingly brazen coyote intrusions in the area and a non-fatal attack on a 5-year-old girl in nearby La Verne in 1979, Wirtz four years ago convinced Claremont and the Humane Society of Pomona Valley to contribute a total of $4,000 to his research in tracking urban coyotes.

With that money, he bought a headset receiver and wildlife collars that emit high-frequency radio signals. He and students eventually trapped four coyotes in the Claremont area, put the collars on them and released them. Daily radio tracking found that the coyotes spend their lives within fairly small areas, with one female never seeming to leave an area of three square kilometers.

The researchers also collected the animals’ droppings. Wirtz says he can pretty much tell what the coyotes ate by seeing what passed through their systems undigested: things like rabbit teeth, cat fur, snake bones, olive pits and aluminum foil. A mini-museum of the remnants of coyote diets is kept on large file cards in a box in Wirtz’s office.

Wirtz said he included the Glendale area in his study only after the 3-year-old girl was mauled to death by a coyote in front of her house in the Chevy Chase canyon area of Glendale in August, 1981. After the incident, county agricultural agents, using a $5,000 emergency appropriation from the Glendale City Council, sharply increased the trapping and killing of coyotes in Glendale. For a while, that produced a regular flow of carcasses for Wirtz to examine.


A Varied Diet

He said he was amazed at what the autopsies revealed: “I found guacamole, fast-food wrappers, cottage cheese, pieces of milk cartons. I hadn’t really expected that at all.”

His study indicated that 37.5% of the diet of Glendale-area coyotes was composed of garbage, with rabbits making up 12.5%, wild birds 10%, cats 10% and field mice 5%. The rest were insects, reptiles, other birds, fruits and plants. The analysis of Claremont coyotes’ droppings found their diet to be 21% rabbit, 26% wild and domestic fruits, 11% insects, 10% birds, 3.8% cats and only 2.5% garbage.

William Harford, executive director of the Humane Society of Pomona Valley, said he thought the study “was worth every penny especially when you get reports of other studies (on other topics) costing hundreds of thousands of dollars and not having as much an impact.”


Wirtz, however, is a bit concerned that his study might be wrongly interpreted in such a way as to increase fears in Glendale and other cities about coyotes. People should keep in mind, he said, that the attack on the Keen girl and the La Verne youngster happened in neighborhoods where residents actually fed the coyotes. They should also remember that the Keen incident was the only recorded fatal mauling of a human by a coyote in North America. And, he said, out of 26,000 animal bites in Los Angeles County last year, only 12 were from coyotes.

“The chances of getting bitten by a coyote are about equal to getting hit by a jet plane,” he said.